1. Field of the Invention
The present invention relates to fluid pressure regulators.
2. Description of the Related Art
In the continuing effort to reduce emissions from motor vehicles, "returnless" fuel systems are seen as a promising way to do so. A conventional fuel system has a fuel line connecting a fuel pump with a fuel rail on the engine of the motor vehicle. Connected to the fuel rail are one or more fuel injectors. A second fuel line runs from the fuel rail to the fuel tank of the motor vehicle to return unused fuel to the fuel tank. This fuel that returns to the fuel tank has often been heated by the heat of the engine. One disadvantageous result from an emissions standpoint is the accumulation of fuel vapor in the fuel tank due to the return of heated fuel.
Returnless fuel systems eliminate the fuel line which returns fuel from the fuel rail to the fuel tank. Instead, the fuel system is designed to supply the proper amount of fuel to the fuel rail, so there is no excess.
In order to regulate the fuel pressure at the fuel rail in a returnless system, a pressure regulator in series with the fuel supply line (a so-called "series-pass" or "demand" regulator) can be advantageous. Being in series with the fuel supply line, such a regulator would not regulate pressure in a more conventional "bypass" manner. Bypass regulators themselves return excess fuel to the fuel tank in the process of regulating pressure.
One proposed design for a series-pass regulator is illustrated in U.S. Pat. No. 5,398,655, issued to Tuckey. Although this design has the potential to be effective as a pressure regulator, other designs may be more manufacturable and less costly. Therefore, alternate designs for series-pass fuel pressure regulators may be advantageous.